There are conventionally battery pack control apparatuses with a function of detecting the spontaneous change of a reference voltage for detecting overcharging and/or overdischarging of a battery pack, a battery pack control apparatus of which is proposed in a first patent document as an example.
When comparing the battery voltage with the reference voltage, the battery pack control apparatus alters the reference voltage relative to a specified voltage in one step. Then, the battery pack control apparatus determines that there is a great spontaneous change in the reference voltage when the relation in magnitude of the reference voltage and the voltage of a unit cell is not reversed irrespective of the relative change of the reference voltage. This makes it possible to detect the spontaneous change of the reference voltage.